Field of the Invention
The present invention relates to a prefabricated modified illumination apparatus for forming fine patterns on a semiconductor device, and in particular, relates to a modified illumination apparatus which forms fine patterns by freely modifying the form of the illumination apparatus, thus improving the resolution of an image.
Generally, in a lithography process, the method of light exposure using modified illumination is capable of forming fine patterns using a formation of incidence of light.
In order to form fine patterns in the prior art, many different modified illumination apparatuses were specifically manufactured. Namely, to form patterns on a wafer having a photoresist layer on its surface, modified illumination apparatuses were appropriately selected so that the exact resolution for forming the fine patterns could be obtained.
Therefore, a variety of illumination apparatuses were made into fixed types before they were used. Then, they were selectively used in order to be suitable for the patterns desired in a semiconductor device.
Referring to FIGS. 1 and 2, a conventional illumination apparatus for forming fine patterns is described.
FIG. 1 is a schematic view illustrating a stepper having a conventional modified illumination apparatus, and FIG. 2 is a schematic view illustrating a structure of a conventional modified illumination apparatus. Numeral 1 denotes light, 2 a modified illumination apparatus, 3 a condenser lens, 4 a photomask, 5 a projection lens, 6 a wafer, 7 a copper plate, and 8 a transmission hole.
As shown in the drawings, light 1 from a mercury lamp passes through the modified illumination apparatus of a predetermined shape. The modified illumination apparatus, shown in FIG. 2, has a transmission hole 8 of a predetermined size in order for the light to transmit through to the copper plate 7. A cross shape in the transmission hole 8 increases the margin of resolution and the depth of focus increases by intercepting some of the light.
The transmitted light from the modified illumination apparatus transmits to a filter (not shown in the figure) which transmits light of a specific wavelength. The condenser lens 3 increases the light intensity, concentrating it on a portion. The condenser lens 3 can be moved back and forth to control the variation of the fine light intensity by controlling the focus of the lens in order to uniformly maintain the intensity of the light. If the light is projected through the photomask, having predetermined patterns on its surface, projection lens 5 shrinks the image. The photoresist layer is exposed so that the pattern is formed on a wafer. Then, a new illumination apparatus suitable for other pattern profiles is manufactured separately since the shape of each of the illumination apparatuses must be varied in accordance with the position of the mask and pattern density in the lithography process, which forms patterns on wafer 6 through a path such as stated above.
Also, since the conventional illumination apparatus is a fixed type confronted with the requirements of a variety of patterns, it is difficult to guarantee a variety illumination. Furthermore, since each of the conventional illumination apparatuses are limited to one shape, use and selection of them is limited and adequate exposure of the wafer can not be insured.
Therefore many conventional illumination apparatuses were made to accommodate a variety of fine patterns, resulting in lost time, expense and space.